Interphase elastic properties of carbon nanotube-epoxy composites and their application in multiscale analysis

Abstract

A multiscale framework was developed to predict the elastic properties of carbon nanotube (CNT)–epoxy composites. The interfacial vacuum layer between the CNTs and epoxy was equivalent to transversely isotropic elastomer. The elastic constants were calibrated based on the interaction energy density in the molecular dynamics simulations; the results exhibited significant differences between these constants. The out-of-plane shear modulus (46.64 MPa) is four orders of magnitude smaller than the in-plane Young’s modulus (362.68 GPa). Subsequently, representative volume elements containing transversely isotropic interphases were developed using the finite element method and analysed comparatively to models without interphases. The results indicated that their difference in the Young’s modulus enhancement ratio was sensitive to the CNT aspect ratio. The enhancement ratio of the model containing the interphase was lower when the CNT aspect ratio exceeded a certain value. This difference increased with increasing CNT aspect ratio and was significant at high CNT aspect ratios (7.35 % when the aspect ratio reached 30). In addition, shear-lag analysis indicated that the interphase increased the interfacial load transfer length. This framework provides efficient interfacial simulations, giving a more accurate prediction of bulk elastic properties and can be extended to a wider range of nanocomposites.

Keywords

• Carbon nanotube
• Epoxy resin
• Interphase layer
• Multiscale analysis
• Representative volume element